The invention relates to a light source apparatus for an endoscope, and more particularly, to such a multi-purpose apparatus for use with a variety of endoscopes.
Endoscopes can be classified into three types according to the synchronization techniques of the still photography, namely, fibrescopes with external still camera, gastrocameras with shutter and viewfinder, and gastrocameras without shutter and viewfinder.
As illustrated in FIG. 1, a fibrescope is essentially comprised of a light guide 1 (a bundle of optical fibres for transmitting illuminating light), and an image guide 2 (a bundle of optical fibres for transmitting a light image) provided with observation lenses 2a, 2b. This permits a normal observation, and where it is desired to take a still photograph of an object 3 such as an affected part within a cavity, an external still camera 4 is attached to the proximal end of the image guide 2 outside the cavity. The still camera 4 comprises a single lens reflex camera of the type commonly used, including a film 5, shutter 6 and synchronization contacts 7. For automatic exposure control of the still photography, there may be provided a half mirror 8 and a light receiving photoelectric transducer element 9 which is connected with an automatic exposure control circuit.
As a feature of the endoscope, the opening and closing of the shutter is not always necessary to perform an exposure control of the film, which may also be achieved by the interruption of illuminating light. For this reason, the exposure control system is contained within a light source apparatus. To this end, the light source apparatus is connected with the fibrescope through a multi-function connector 10 which permits simultaneous connection of optical, electrical and pneumatic (not shown) media between the apparatus and the endoscope. The connector 10 is also used in a gastrocamera to be described later, permitting a common use of the same light source apparatus with the fibrescope. The fibrescope may also be utilized for viewing an affected part through a cine camera or a television camera. In such instance, the cine camera or television camera replaces the still camera 4. The transducer element 9 may be utilized during such use to control the illumination of a film surface to a constant value, by adjusting the light source.
A gastrocamera includes a camera mechanism mounted in the distal end of an endoscope and which can be remotely operated from the exterior to achieve a photographing and a film winding operation. As mentioned previously, there are two kinds of gastrocameras, those including and not including a shutter and a viewfinder. In either kind of gastrocamera, there is no governor for controlling the shutter speed of the camera, and the exposure period is controlled by a manual operation, so that the use of synchronized photographing well known in the art of ordinary cameras is precluded.
Where an automatic exposure control is intended, the calculation of the exposure period and the synchronization of the film exposure are the two most important factors requiring a special synchronizing arrangement in the light source. Usually, a film used in the gastrocamera has a width on the order of four or five millimeters, and hence a commercially available ordinary film cannot be directly used in the gastrocamera. Special film requirements, quantity sold and the developing process required limit the variety of films, including those used with daylight and those used with tungsten lamps. When providing one of these films and using a light source of the opposite kind, it is necessary to correct the color temperature by inserting a color conversion filter. Also, it may be necessary to use a film speed constant which is different from that used with the fibrescope. Additionally, the absence of a shutter speed controlling governor may cause an extended exposure period when taking a picture in dark place, which may result in a blurring of the image to produce an unusable photograph. Thus it will be seen that the light source apparatus must accommodate for these requirements, a feature requiring a special attention to the gastrocamera in contradistinction to the fibrescope.
FIG. 2 shows an exemplary gastrocamera with shutter and viewfinder while FIG. 3 illustrates an exemplary gastrocamera without shutter and viewfinder. In these Figures, corresponding elements are designated by like reference characters. In either arrangement, the gastrocamera includes a light guide 1A for transmitting illuminating light to an object 3 such as an affected part in a cavity, the reflected light of which is passed through an objective 2c onto a film 5A for exposure. The film 5A is drawn from a cartridge 16, and a film winding takes place through a string 12 by a remote control. The connection with the light source apparatus is accomplished through a multi-function connector 10 in a manner similar to that of the fibrescope.
The gastrocamera of FIG. 2 includes an image guide 2A which permits a normal viewing operation. A shutter 6a is disposed in front of the film 5A since otherwise the viewing light will cause an exposure of the film 5A. The shutter 6a is adapted to be remotely controlled by a string 11 which is disposed around a drum 13. A pair of switch operating projections 14a, 14b are mounted on the drum 13 for cooperation with synchronizing switches 7a, 7b. The arrangement is such that the switch 7a is actuated by the projection 14a immediately before the shutter 6a begins to open while the projection 14b actuates the switch 7b immediately after the shutter 6a has opened. These switches are maintained in their actuated position until the shutter 6a returns after the completion of a photographing operation. The two synchronization signals generated by the switches 7a, 7b serve as the means for clearly defining the period during which the shutter continues to move inasmuch as the shutter 6 a is manually operated. These signals are effectively used when the gastrocamera is coupled with the light source apparatus according to the invention.
A combination of half mirror 8 and photoelectric transducer element 9 operates in a manner similar to that of the fibrescope for the purpose of automatic exposure control. A resistor 15 is connected with the multi-function connector 10 for discriminating the kind of the endoscope, and is effective to indicate to the light source unit that the endoscope coupled therewith is one having a shutter and viewfinder.
In the gastrocamera of FIG. 3, neither the image guide nor the shutter as shown in FIG. 2 are present. This is because no viewing operation is performed and hence there is no need for a shutter which shields light from the film 5A. A synchronizing switch 7c is closed when taking a still photograph to permit an illumination of the object 3 through the light guide 1A. The reflected light from the object impinges on the transducer element 9a to control the exposure period. A switch 7d is provided to enable the detection of the position of the inserted gastrocamera. Because the gastrocamera of FIG. 3 is not provided with a viewfinder which would normally indicate the depth of the camera when inserted into a cavity in a human body, a temporary illumination is activated through the switch 7d while observing the surface of the physical body of a patient whose clothes have been removed so that the camera position within the cavity may be located by viewing a bright region along the body through which the light leaks.
The synchronizing switch 7c is interlocked with a film winding mechanism, not shown, which feeds the film 5A one frame for each closure thereof. However, the switch 7d operates alone, minimizing a waste in the film which occurs as a result of its exposure by the locating illumination. A short circuit 15d across selected pins of the multi-function connector 10 is shown, and is provided for the discrimination of the kind of the endoscope, serving to indicate to the light source apparatus that the gastrocamera connected therewith has no shutter and viewfinder.
As will be noted from the foregoing description, the synchronization technique for still photography is different for each of the described kinds of the endoscopes even though any of these endoscopes can be connected with the light source apparatus through the multi-function connector. However, the adjustment of illumination, automatic exposure control for the still photography as well as the cine and television cameras vary from endoscope to endoscope, requiring a manual intervention and causing inconveniences.